Studies of arterial lesions in children and young adults: In order to minimize observer bias, studies of all age groups will be carried out "blind". Emphasis will be on the nature of early chemical and conformational changes and the sequence of these alterations. New techniques developed during the year will be applied to current studies and to completed cases where indicated. Observations will be correlated with data on age, sex, race and clinical history, esp. family history of cardiovascular diseases. Polarization microscopic studies of stained myosins in striated and smooth muscle, esp. in cardiovascular lesions, will be continued. Fluorescence microscopic studies of stained cardiovascular lesions will include visible fluorescence with long wave exciting light and infrared fluorescence. Polarized fluorescence and fluorescent brightening agents will also be used. Development of new methods for demonstration of early chemical and structural alterations of fibrous proteins; iodinated, reactive, and neutral premetallized dyes will be tested. Myoepithelial cells and myofibroblasts: The microscopic properties of smooth muscle and of myoid material in various epithelial and connective tissue cells will be compared.